LOCAL-STRUCTURE OF CU2-CU2+ (M=CD, MN) LAYER PEROVSKITES - INFLUENCE OF HYDROSTATIC-PRESSURE IN THE 0-60 KBAR RANGE( IN THE (C2H5NH3)(2)MCL4)

This paper deals with the effects of pressure on the charge-transfer s pectra of CuCl64- complexes formed in Cu2+ doped (C2H5NH3)(2)MCl4 (M = Cd, Mn). A pressure-induced redshift is observed for the first charge -transfer band in both crystals. While the shift is continuous for the Mn crystal at a rate of -40 cm(-1)/kbar in the 0-60 kbar range, it ex periences an abrupt jump of -1400 cm(-1) around 26 kbar for the Cd cry stal. Such a discontinuous behaviour is interpreted in terms of a stru ctural change in the CuCl64- coordination geometry from an axially elo ngated octahedron to a more compressed geometry. The present results a re compared with those reported for the pure (C2H5NH3)(2)CuCl4 crystal .